REPRODUCTIONRESEARCH BMP15 regulates the inhibin/activin system independently of ovulation rate control in sheep Anthony Estienne1, Belén Lahoz2, Peggy Jarrier1, Loys Bodin3, José Folch2, José-Luis Alabart2, Stéphane Fabre3 and Danielle Monniaux1 1UMR85 PRC, INRA, CNRS, IFCE, Université de Tours, Nouzilly, France, 2Unidad de Producción y Sanidad Animal, Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Instituto Agroalimentario de Aragón – IA2 (CITA-Universidad de Zaragoza), Zaragoza, España, and 3GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France Correspondence should be addressed to D Monniaux; Email:
[email protected] Abstract Polymorphisms in the gene encoding bone morphogenetic protein 15 (BMP15) have been associated with multiple ovulations in sheep. As BMP15 regulates inhibin expression in rodents, we assumed that the ovarian inhibin/activin system could mediate part of the effect of BMP15 mutations in the regulation of ovulation rate in sheep. To answer this question, we have studied the effects of two natural loss-of-function mutations of BMP15 on the expression of components of this system. The FecXR and the FecXGr mutations, when present respectively in Rasa Aragonesa ewes at the heterozygous state and in Grivette ewes at the homozygous state, were associated with a twofold increase in ovulation rate. There were only small differences between mutant and wild-type ewes for mRNA expression of INHA, INHBA, ACVR1B, ACVR2A, FST or TGFBR3 in granulosa cells and inhibin A or activin A concentrations in follicular fluid. Moreover, the effects of mutations differed between breeds. In cultures of granulosa cells from wild-type ewes, BMP15, acting alone or in synergy with GDF9, stimulated INHA, INHBA and FST expression, but inhibited the expression of TGFBR3.